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This is a philosophical question. Over the last few years, many of the household devices, particularly those that are more mobile and etc are DC devices. Are we at some point where a DC household may become a possibility and Edisons dream might come true??

The array of DC devices

  1. Internet stuff - routers, modems
  2. Most complex computer electronics - Desktops, laptops, NAS, phones, tablets, gaming consoles, etc
  3. Lighting - LED
  4. More that I cant think of or perhaps know which also convert AC -> DC

Problems with AC

  1. Each device needs its own power supply ( AC-> DC power brick). This is
    a) Unpleasant to look at and deal with, and
    b) a costly point of failure.

  2. Each power brick may or may not be optimized, as far as power conversion goes.

Alternative - A central (or a few ) high capacity power adapter which converts the AC into a DC power grid for the house which can then be tapped directly by the various devices. This eliminates the need for the power brick, and hopefully the central power adapter is of state of the art, and can be upgraded seperately from the devices, as needed.

Need standardization of:

  1. Device voltage. Currently devices use 5/ 9 / 12 or others I may not be aware of, for this idea to work they need to work with one particular one, unless switching between voltages is cheap enough, or multiple DC lines are provided.
  2. Power socket input. Each device appears to have its own input socket type, this should standardize if the power supply cable should be comoditized, perhaps USB - C will play a part here.
Karthik T
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    We are not a discussion site. This is a question for philosophers. :) – Passerby Apr 04 '16 at 07:25
  • @Passerby what might be a good place for such a question? This question can be made a bit more concrete by just answering what stands in the way of this idea? – Karthik T Apr 04 '16 at 07:30
  • I'm no philosopher but I can sill refute the idea easily with some hard-core engineering facts, see my answer. – Bimpelrekkie Apr 04 '16 at 07:34
  • A power brick provides galvanic isolation from power mains supply and user - what would replace this obvious safety feature? Voting to close this mumbo jumbo. – Andy aka Apr 04 '16 at 07:37
  • related (but not a direct duplicate): [Why are the power transmission distribution systems AC and not DC](http://electronics.stackexchange.com/questions/64604/why-are-the-power-transmission-distribution-systems-ac-and-not-dc/) – helloworld922 Apr 04 '16 at 08:20
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    Generally DC is only good for distances of less than 5m (16ft) and generally start losing efficiency for distances of around 2m (6ft) so an all-DC house starts to make sense if people start living in doll houses. – slebetman Apr 04 '16 at 09:02
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    What seems to be becoming more common is AC outlets with built-in USB power supplies for convenience - effectively hiding the power brick in the wall. – pjc50 Apr 04 '16 at 09:02
  • *"This a philosophical question"*. At least that makes closing this a no-brainer without having to read farther. We don't do philosophical questions here. -1 for obvious violation of the rules. – Olin Lathrop Apr 04 '16 at 10:55
  • DC is LESS flexible than AC. Low voltage at more than minimal power causes either high losses or expensive wiring. Heating at LV is not viable. One HVDC voltage in house would then need converters as before with less advantages than AC;. || Edison had some great abilities but was also a moron in some areas. This was one such. – Russell McMahon Apr 04 '16 at 12:30
  • Did you know that devices powered by 5V or 12V actually step down the voltage internally even lower? A modern CPU might run at about 1 volt and 30 amps. You can't distribute that over *twenty centimetres*, much less through a house. They put multiple converters *in the computer*, as close as possible to the chips that are using the power. – user253751 Feb 05 '19 at 03:55

2 Answers2

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Edisons dream might come true

No because Edison wanted to distribute power (over long distance) using DC which is cumbersome and lossy. That's why we use AC. The appliances you talk about take only limited amounts of power. Using a DC distribution system for that is also lossy even over the short distances inside your house. To limit the power loss thick (copper) cables would be needed making it an expensive solution.

Your "problems with AC" are not really problems if you see how cheaply we can now make power adapters. And although maybe not optimized I bet it is still more efficient that having a "low voltage DC distribution bus" running around your house. This is due to the cost of copper as I mentioned above. And you need thick copper to limit voltage drop = power loss.

Bimpelrekkie
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  • yeah I am ignoring the "distribute" part of the dream, Although that seems to be coming true in bits as well - http://www.nytimes.com/cwire/2009/06/15/15climatewire-companies-reconnect-edisons-dream-of-direct-c-5867.html?pagewanted=all – Karthik T Apr 04 '16 at 07:33
  • It is for the power loss that I thought perhaps one per room might be more effective? – Karthik T Apr 04 '16 at 07:36
  • Sure but not that how that is only for **specific** applications, only **part** of the distribution length (mainly: the part that is under water). Also: nothing new: there's been a DC line between Denmark and Norway (I think) for some years already. – Bimpelrekkie Apr 04 '16 at 07:36
  • No one per room is still inefficient unless you need only very little power maybe. But don't underestimate how good the efficiency of a properly designed wall adapter can be: 90 % or so. And the power levels are low in general so there's not much to gain. 10% loss on a few watts is almost nothing. – Bimpelrekkie Apr 04 '16 at 07:39
  • I was correct: https://en.wikipedia.org/wiki/Skagerrak_(power_transmission_system) operating since 1977: **nothing new here !** If only the NY times would have done their research... – Bimpelrekkie Apr 04 '16 at 07:46
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    Why is DC transmission more lossy than AC? – Chu Apr 04 '16 at 08:16
  • Thanks for that link, very interesting reading. I am going to accept this answer, but I feel there is a small missunderstanding, my idea doesnt eliminate the 10%, but ensures that it is at most 10% for all devices, and perhaps gives you a simpler upgrade to a hypothetical 5% loss power supply when it comes around. – Karthik T Apr 04 '16 at 08:16
  • @Chu It's not more lossy than AC _per se_, the problem is that you have 110/220VAC in house, and you want 5 to 12VDC in your devices. Running 220VDC would still require converters everywhere, so you still have your DC adaptors everywhere. Running 12VDC is extremely lossy. – yo' Apr 04 '16 at 09:41
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    @Chu Basically electric **current** is the problem, current gives power loss so to distribute power over a distance you want low current. With AC you can use a transformer to increase the voltage and this **decreases the current**. That is why power is distributed (over land) using high voltage AC. Under water capacitance to water is an issue so there High voltage DC is used. However, it is more complex/expensive to make / use high voltage DC compared to AC. So that is why High voltage DC is only used under water. – Bimpelrekkie Apr 04 '16 at 09:46
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    @yo' It's quite easy to get AC from DC and then convert to whatever you need in the domestic environment. More importantly, transmission by DC means you don't have the losses associated with the reactive component of current in the transmission lines. – Chu Apr 04 '16 at 10:15
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No

While low power devices (like smart phones or routers) are common, there are many high power devices in an average home: hoover, hair dryer, lawn mower, etc. In fact, compared to a smart phone, even just a laptop needs a lot of power.

Power = Current * Voltage. You don't want high current as you then need thick wires. So high voltage makes sense for high power devices - which is exactly what current AC sockets give you. It is easier to change AV voltage than DC, because transformers work with AC. With modern electronics, transforming DC voltage is practical, so in theory you could have a high-voltage DC system. But there's just no point - it works better with AC.

Anyway, there is already a solution to get rid of the annoying power bricks:

enter image description here

paj28
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    I'd never buy something like this because if the build-in 5V supply breaks and starts smoking, I cannot quickly disconnect it from the mains. I simply do not want any mains-connected electronics to be connected to the mains permanently. – Bimpelrekkie Apr 04 '16 at 11:21
  • @FakeMoustache - did you just downvote me because you don't like these USB sockets? – paj28 Apr 04 '16 at 11:29
  • Nope that was someone else – Bimpelrekkie Apr 04 '16 at 12:00
  • Are you surprised of an opinion-based downvote when answering an opinion-based question? – Dmitry Grigoryev Apr 04 '16 at 12:03
  • @DmitryGrigoryev - no opinions here, just solid facts :) – paj28 Apr 04 '16 at 12:14
  • @FakeMoustache - fair enough. Many lighting circuits also have permanently connected transformers. And if they do start smoking? Turn the circuit off - that's a quick way to disconnect. Really, I think you're making life hard for yourself with self-imposed limitations like that. – paj28 Apr 04 '16 at 12:15
  • @paj28 A transformer I do not categorize as "electronics" (no active elements) so a transformer would be OK by my standards. You say: *Turn the circuit off* yes but, that is the problem, you cannot as it is always connected to mains. OK, what I meant was that the 5V adapter circuitry inside the socket starts smoking, not the device charging from it. I do not mind a separate adapter so my life isn't any harder :-) – Bimpelrekkie Apr 04 '16 at 12:20
  • @FakeMoustache I don't put any trust in my ability to unplug something from mains in case of failure. I only trust fuses. – Dmitry Grigoryev Apr 04 '16 at 12:23
  • @FakeMoustache - I meant, turn it off at the switch box – paj28 Apr 04 '16 at 12:26